The demand for energy and the hydrocarbons from which that energy is derived is continually rising. The hydrocarbon raw materials used to provide this energy, however, contain difficult to remove Sulfur and metals that hinder the processing of these materials and thus limit their usage as an energy source. Additionally, Sulfur can cause air pollution when hydrocarbon sources such as gas or oil are consumed. Sulfur can poison catalysts designed to remove hydrocarbons and nitrogen oxide from motor vehicle exhaust. Thus hydrocarbon sources such as crude oil, bitumen, heavy oil, oil products, or portions thereof such as residues, vacuum residues, and distillates are treated to remove unwanted items such as Sulfur or nitrogen.
Over the last several years, sodium has been recognized as being effective for the removal or reduction of Sulfur from hydrocarbon sources that would otherwise be unusable due to the high Sulfur content. Sodium is capable of reacting with Sulfur and other constituents in the hydrocarbon source, including any contaminants that may be found in the hydrocarbon source, to dramatically reduce the Sulfur and other unwanted items such as nitrogen. The Sulfur reduction is accomplished through the formation of sodium sulfide compounds such as sodium metal sulfide, polysulfide and hydrosulfide. Other alkali metals such as Lithium have also shown to be effective in the same way.
However, other metals, including heavy metals, contained in the hydrocarbon source can inhibit or prevent the process of removing unwanted materials such as sulfur or nitrogen from the hydrocarbon source. For example, heavy metals can poison catalysts typically utilized for removal of Sulfur through standard and improved hydro-desulfurization processes whereby hydrogen reacts under extreme conditions to break down the Sulfur bearing organo-sulfur molecules. At a minimum, this can make the desulfurization or denitrotization of the hydrocarbon source prohibitively expensive. Thus it is also desirous to remove heavy metals contained in the hydrocarbon source.
Heavy metal may be removed from hydrocarbon sources using alkali metals such as sodium or lithium. Heavy metals contained in organometallic molecules such as complex porphyrins are reduced to the metallic state by the alkali metal. Once the heavy metals have been reduced, they can be separated from the hydrocarbon source because they no longer are chemically bonded to the organic structure. In addition, once the metals are removed from the porphyrin structure, the nitrogen heteroatoms in the structure can be exposed for further denitrogenation.
The resulting byproduct of the treatment of hydrocarbon sources using alkali metal to remove Sulfur or other unwanted materials such as heavy metal can be a feed stream that contains alkali metal sulfides and polysulfides and amounts of heavy metal. The treatment of hydrocarbons using alkali metal is expensive because of the cost of the raw materials needed. However, if the alkali metal could be recovered and reused, it would limit the costs. Further, if Sulfur could be recovered from this byproduct feed stream, it would further reduce the treatment costs and could possibly become a source of revenue.
One problem, however, in the recovery of alkali metal and Sulfur from solution created as a result of desulfurization or demetalization processes, is that this solution feed stream also contains non alkali metals, such as heavy metals, that hinder, inhibit, or prevent the alkali metal and Sulfur recovery process.
Thus it would be an advantage to provide a method and apparatus to facilitate separation and recovery of the alkali metal and Sulfur from feed streams, regardless of the presence of heavy metals in the feed stream. It would be another advantage to provide such a recovery of the alkali metal and Sulfur efficiently using in a single process and system.